Refrigerating apparatus



March 5, 1940. R, E TQBEY 2,192,849

REFRIGERATING APPARATUS Filed May ll, 1958 WIT ESSES:

INVENTOR 4/ RAYMOND E TossY ci n. y BY 25 I ATTORNVA/ Patented Mar.. 5 1940 UNITED STATES PATENT OFFICE REFRIGERATING APPARATUS Pennsylvania Application May ll, 1938, Serial No. 207,247

17 Claims.

My invention relates to refrigerating apparatus .and has for"an object to provide improved apparatus of thiskind.

A further object of the invention is to main- 5 tain the temperature within a refrigerated zone substantially constant irrespective of changes in temperature exteriorly of the zone, which temperature changes vary the amount of heat leakage into the zone.

l lit is a further object of the invention to vary the operation of a refrigerating mechanism in response to variations in temperature of the ambient atmosphere so that the temperature of the refrigerated zone is maintained substantially conl stant.

llt is a further object of the invention to maintain the temperature differential of the refrigerant evaporator and the temperature ofthe air cooled thereby within closer limits than has been effected heretofore.

It is a still further object of the invention to control the operation of a. refrigerating machine by a thermostat subjected-to the temperature of the high pressure condensed refrigerant prior to its admission into the evaporator structure and, furthermore, to subject the thermostat to the temperature of the `low pressure condensed refrigerant prior to its admission into the evaporator.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing, forming a part thereof, in which:

Fig. 1 is a diagrammatic view of a refrigerating machine constructed and arranged in accordance with my invention;

Figs. 2 and 3 are respective side and end views of an element of the control apparatus employed 40 in Fig.l l;

Figs. 4 and 5 are respective side and end views of a modified form of control element shown in Figs. 2 and 3; and

Fig. 6 is a side view of another form of the control element applied to a conventional evaporator.

Referring now to Fig. l of the drawing, I have shown my invention applied to a refrigerator of 50 the domestic type, including an insulated cabinet structure Il! that encloses a compartment or zone III to be refrigerated. Heat is abstracted from the air in the zone II by means of an evaporator I2 of conventional sheet metal construction which includes an inlet conduit I3 for condensed refrigerant and an outlet conduit I4 for refrigerant vaporized in the evaporator.

Circulation of refrigerant through the evaporator is effected by a refrigerating machine, generally indicated at I5, which preferably operates on the compressor-condenser-expander cycle. The refrigerating machine I5 includes a compressor I6, driven by an electric motor I1. A condenser I8 is cooled by the ambient air which is circulated by a fan I9. Refrigerant vaporized in the evaporator l2 is withdrawn therefrom through the conduit I4 by the compressor I6 and is compressed to a relatively high pressure. The compressed refrigerant is delivered to the condenser I8 through a conduit 2l. Refrigerant liquefied in the condenser I8 is conveyed to the inlet conduit I3 of the evaporator through a suitable expansion device, such as, for example, a capillary tube 22. The capillary tube 22 operates to reduce the relatively high pressure of the condensed refrigerant to the pressure maintained in the evaporator l2 by the compressor I6, as is well understood.

The capillary tube 22 includes an elongated passage of fixed ow area (not shown) which restricts the flow of refrigerant and effects a reduction in the pressure thereof. The inlet of the tube 22 may be connected to the condenser by a conduit 20 as shown.

As described hereinafter, the refrigerating machine IG is controlled thermostatically to maintain the temperature of the evaporator I2 at predetermined values that are adjusted by changes in the temperature of the ambient atmosphere exteriorly ofthe zone II. The compensation is such that the \mea.n temperature of the evaporator I 2 varies inversely with changes in the temperature of the ambient atmosphere. The different rates of heat leakage into the zone Il caused by ambient temperature changes are, therefore, vcompensated for by various rates of heat absorption effected by the evaporator I I.

Preferably, a thermostat of the expansiblefluid type, shown generally at 23, is employed for controlling operation of the compressor I6. The thermostat 23 includes an expansible bellows 2l connected by a tube 25 with a bulb' 26, which elements define a closed chamber for an expansible uid. Preferably, a volatile fluid whose pressure is a function of the temperature of the bulb 26 is employed. The thermostat 23 includes a pivoted arm 21 that is actuated by the bellows 24 and biased by a spring 28. 'I'he arm 21 operates a switch 29, preferably by means of a snap-acting mechanism 3l, so that the switch 29 is opened.

circuit L1--L2.

and closed, respectively, in response to predetermined low and high pressures in the bellows 24 and, therefore, predetermined low and high temperatures of the bulb 26. An adjustment 30 may i be provided for varying the bias of the spring 26 and, therefore, the temperatures of the bulb 26 at which opening and closing of the switch 29 are effected. 'Ihe switch 29 controls energization of the motor I1 that is connected to an electric As the construction and operation of adjustable fluid type thermostats are well understood in the art, further description of the .same is deemed unnecessary.

In the copending application of Leslie B. M. Buchanan, Serial No. 122,505, filed January 27, 1937, and assigned to the assignee of the present application, there is disclosed and claimed a refrigerating system of the type set forth heretofore wherein the mean temperature of the S0 evaporator is varied inversely in response to ambient temperature changes. In this application, the thermal responsive element of the control responds to the temperature of the refrigerant in the evaporator and is disposed in heat transfer 26 relation with the condensed refrigerant admitted to the capillary tube, the temperature of the condensed refrigerant being a function of ambient temperature. As the iiow of condensed refrigerant substantially ceases during inactive periods 30 of the machine, the compensation eiiected by the condensed refrigerant prevails only during active periods of the machine and, therefore, it is only the cut off" temperature of the evaporator, i. e., the temperature at which the compressor is stopped, which is effected by ambient temperature changes. The present invention defines an improvement of the system claimed in said copending application in that both the cut off and cut on" temperatures of the evaporator are varied as the outside or ambient temperature varies. The cut on temperature is the temperature of the bulb at which the compressor is started.

In practicing the present invention, the thermostatic bulb 26 is secured to a member 33 of metal or other heat conducting material, which member 33 may be disposed in the zone II. The member 33 is disposedin heat transfer relation with the low temperature refrigerant in the evaporator I2 and with the condensed refrigerant in the inlet end of the capillary tube 22, the temperature of the latter being a function of outside temperature. Preferably, the member 33 is connected to the inlet conduit I3 of the evaporator. which is of low heat storage capacity compared to the main body of the evaporator and, therefore, responds more quickly to changes in lthe temperature of the refrigerant-therein. Obviously. other portions of the evaporator I2 may be 50 connected to the member 33 if desired. The tube 22 and the bulb 26 may be secured to the member 33 by a clamp 34 and the inlet conduit I3 of the evaporator may be soldered or otherwise secured to the member 33 in proximity to the bulb 26 e5 as shown in Figs. 2 and 3.

During active periods of the apparatus, heat is transferred to the member 33 and the control bulb 26 from the vcondensed refrigerant in amounts varying with the temperature of the am- 70 bient atmosphere. Heat is abstracted from the member 33 and the control bulb 26 by the low temperature refrigerant in the evaporator inlet conduit I3. When the outside temperature is relatively high, heat is imparted to the member '75 33 and bulb 26 at a relatively high rate lo that the compressor must operate to depress the temperature of the evaporator I2 to a relatively low value before the control bulb 26 is cooled suiiiciently to terminate operation of the compressor. When the outside temperature is relatively low, less heat is imparted to the member 33 and control bulb 26 so that the latter is cooled to the temperature at which it terminates operation of the compressor when the evaporator temperature is at a higher value.

While the temperature of the portion of the member 33 in contact with the bulb 26 is substantially the same as the bulb temperature, the average temperature of the member 33 as a whole and the amount of heat stored therein are higher when the outside temperature is high than when the outside temperature is low. Heat, therefore. is continuously imparted. to the bulb 26 by the member 33, the rate of heat transmission varying with the average temperature of the member 33, and, therefore, the 4temperature of the exterior atmosphere.

During inactive periods of the compressor, the supply of heat to the member 33 is terminated as the ow of condensed refrigerant ceases. The temperatures of the evaporator I2 and the control bulb 26 increase due to the heat load in the zone II. The member 33 which has stored heat during the operating period of the compressor imparts heat to the control bulb 26 and assists in raising its temperature. Accordingly. when the temperature of the member 33 is high due to a high ambient temperature, the control bulb 26 will be heated to its cut on temperature sooner than when the temperature of the member 33 is low or when the ambient temperature is low. Accordingly, both the "cut on and cut off temperatures of the evaporator I2 vary with variations in the ambient temperature.

The control bulb 26 is disposed contiguous to the evaporator inlet conduit I3 and responds to both the temperatures of said conduit and the member 33. The temperature of the member 33 is affected by the temperatures of the evaporator conduit I3 and the capillary tube 22. The member 33 defines-'a heat storage body which imparts more or less heat to the control bulb 26 during inactive periods of the machine, depending upon thetemperature of the outside atmosphere. It will be understood that operation of the compressor I6" is started and stopped when the temperature of the bulb 26 attains predetermined values, which values are determined by the position of the adjustment 36 and bias of the spring 26. The temperatures of the bulb 26 at which the compressor is started and stopped are the same for -a given position of the adjustment 36 regardless of the ambient temperature.

My improved control apparatus provides compensation for varying heat loads in the zone Il due to periodic opening of the access door thereof or to varying amounts of heat in the articles to be cooled. As the member 33 and control bulb 26 are subjected to the air in the zone Il. their temperatures are affected by the temperature-of the air. As the temperature of the air in the zone II increases due for example, to the 4insertion of relatively warm products therein, the rate of heat flow to the bulb 26 and conduit i3 increases so that the rise in the temperature of the bulb 26 to the "cut on" value is expedited. Accordingly, the control bulb 26 is affected by the temperature of the cooled air in addition to the temperatures of the liquid conduit I3 and the capillary tube 22.

amasar;

Operation As shown in Fig. l, the refrigerant condensing unit l is inactive as the temperature of the bulb 26 is below the value at which it effects closing of the thermostatic switch 29. When the temperature of the bulb 26 is increased to a predetermined value. for example, 35 F., the thermostatic switch 29 is closed and operation of the condensing unit i5 is initiated. Translation of vapor from the evaporator I2 to the condenser it is therefore effected by the compressor i6. The pressure Within the condenser It rapidly increases to a value at which condensation is effected. The condensed refrigerant passes from the condenser i6 through the conduit 26 and capillary tube 22 to the evaporator inlet conduit i3.

The temperature of the refrigerant entering the capillary tube 22 bears a direct relation to the temperature of the ambient atmosphereand imparts heat to the heat storage member 38 and the thermostatic bulb 26 at a rate determined by the ambient temperature. The temperature of the evaporator inlet conduit I3 is rapidly depressed subsequent to the starting of the condensing unit i5 and heat is abstracted thereby from the member 33 and thermostatic bulb 26. When the temperature of the ambient atmosphere is relatively low, for example, 65 F., the amount of heat imparted to the member 33 is relatively low. Accordingly, the cold evaporator conduit I3 depresses the temperature of the bulb 26 in a relatively short period of time to the value, for example, F., at which the thermostatic switch 29 is opened, so that the compressor runs only a short time. Accordingly, the refrigerating temperature of the evaporator at the time the compressor is stopped is relatively high in a 65 ambient atmosphere. i

During the inactive period of the condensing unit |16, the temperature of the bulb 26 is increased due to the heat load in the box and to 'a relatively small amount of heat which is iml partedther'eto by the member 33, which heat has been stored in the member 33 during the active period of the compressor. When the temperature of the bulb 26 has attained a value of 35 F., the switch 29 is closed and circulation of refrigerant is initiated.

. so that the temperature of the evaporator` I2 and y its conduit I3 must be depressed to a relatively low value by longer operation of the compressor t6 in order to abstract sufficient heat from the bulb 26 to depress its temperature to the cut oir l value of 20 F. The temperature of the evaporator l2 at the time of starting the compressor is also lower than when the ambient temperature is low because of the more rapid heating of the bulb 26 to its cut on temperature by the member 33, it being understood that the temperature of the member 33 and the amount of heat stored therein are relatively high when' the ambient temperature is high.

Accordingly, the temperatures of the evapolrators at the time of both starting and stopping of the compressor are lower when the outside temperature is high than when the outside temperature is low. The system, therefore, operates to maintain a substantially constant temperature dierential, while increasing and decreasing the mean evaporator temperature. This result I obtain by employing a heat storage member of suitable mass having the thermostatic element secured thereto, which member is heated and cooled by the condensed and evaporated refrigerant, respectively.

As set forth heretofore, the control bulb 26 is affected by varying temperatures of the air in the compartment H due to different heat loads.-

The insertion of a relatively warm article to be refrigerated in the compartment II increases the air temperature, which change is reflected by the conduit i3 and control bulb 26 prior to the change in temperature of the body of the evaporator I2.l Accordingly, by connecting the bulb 26 to a portion of the evaporator of low heat storage capacity, changes in temperature of the evaporator I2 due to varying heat loads are anticipated by the control bulb 26.

The compensating effect produced by the capillary tube may be varied by releasing the clamp 34 and adjusting either the control bulb 26 relative the evaporator inlet conduit' I3 or the capillary tube 22 relative the control bulb 26. In either event, the effect of the capillary tube in heating the bulb 26 is varied and, therefore, the compensating effect produced by the tube 22 is varied.

In Figs. 4 and 5, a second embodiment of the invention is disclosed wherein a heat storage member 4I is provided having a slot 42 formed therein. The evaporator inlet conduit I3 is soldered or otherwise axed to the member 4I within the slot 42. A separate plate 43 is secured to the member 4I by a screw 44 which plate 43 has the capillary tube 22 soldered or otherwise secured thereto. Ihe control bulb 26 is clamped between the plate 43 and the member 4I and responds to the temperature of both of these elements. The operation of the refrigerating apparatus employing either of the embodiments is similar.

A third embodiment of the invention is shown in Fig. 6 wherein a heat storage member 45 is secured directly to an evaporator 46. The capillary tube 22 and control bulb 26 are secured to the member 45 in any suitable manner, such as, for example, by soldering. The member 45 is provided with one or more slots ,41, Within which screws 48 are disposed, which screws 46 are threaded in' the evaporator structure 46. Adjustment of the member 45 and, therefore, the bulb 26. relative to the evaporator 46 is provided by the sliding connection between the member 45 and the evaporator 46. Accordingly, if the capillary tube is overcompensating, the member 45 and bulb 26A may be moved closer to the evaporator 46 so that the control bulb 26 is cooled more rapidly. Conversely, if the capillary tube is under-compensating, the control bulb 26is moved away from the evaporator so that heat from the capillary tube has greater eii'ect in warming the control bulb and e'ects lowerevaporator temperatures at the time the compressor is started and stopped.

From the foregoing description, it will be apparent that I have provided improved refrigerating apparatus wherein compensation for different rates of heat leakage into the refrigerated zone due to varying temperatures exteriorly of therefrigerated zone is provided. The mean temperature of the evaporator is varied inversely with outside temperature changes while maintaining the temperature differential of the evaporator at a substantially constant value. Furthermore, the control apparatus readily responds to variations in the heat load in the refrigerated zone whereby the temperature of the evaporator is adjusted to compensate for said variation in an anticipating manner.

While I have shown my invention in several forms, it will be obvious to those skilled in the art thatit is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed 'thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

l. In refrigerating apparatus, the combination of means defining azone to be refrigerated, an evaporator for abstracting heat from said zone,. means for circulating refrigerant through the evaporator, a heat storage member, means for imparting heat to a portion of said member in response to changes in temperature of the air exteriorly of said zone, means for abstracting heat from a second portion of said member in response to the temperature of the evaporator and means responsive to the temperature of a portion of the heat storage member for controlling the operation of the refrigerant circulating means.

2. In refrigerating apparatus, the combination of refrigerant condensing and evaporating means, means for circulating refrigerant through the condensing and evaporating means, means for passing air in vheat transfer relation with the o condensing means for abstracting heat from the latter, whereby the temperature of the condensed refrigerant is a function of the air temperature. a heat storage member disposed in heat transfer relation with both the condensed refrigerant and the refrigerant in the evaporator, and means responsive to the temperature of a portion of said member for controlling the operation of the circulating means.

3. In refrigerating apparatus, the combination of a refrigerant evaporator, a condenser, means for translating air over the condenser for cooling the same, means for translating refrigerant vaporized in the evaporator to the condenser for liquefaction, means having an elongated passage 'of fixed fiow area for conveying the condensed refrigerant` from the condenser to the evaporator, a heat storage member disposed in heat transfer relation with the lastmentioned means and with the refrigerant in the evaporator, and means responsive to predetermined high and low temperatures of the heat 'storage member for initiating and terminating operation of the refrigerant translating means.

4,. 'Ihe combination as claimed in claim 3 includingmeans for varying the rate of transfer of heat between the condensed refrigerant conveying means and the heat storage member.

5. In refrigerating apparatus, the combination of refrigerant condensing and evaporating means, means for circulating refrigerant through the condensing and evaporating means. means for passing air in heat transfer relation with the condensing means for abstracting heat from the latter, whereby the temperature of the condensed refrigerant is a function of the air temperature, a heat storage body disposed in heat transfer relation with both the condensed refrigerant and the refrigerant in the evaporator, means for varying the rate of transfer between the heat storage member and one of said bodies of refrigerant and means responsive to the temperature of the heat storage body for controlling the operation of said refrigerant circulating means.

6. In refrigerating apparatus, the combination of means defining a zone to be cooled, a refrigerant evaporator for abstracting heat from said zone, means for withdrawing vaporous refrigerant from the evaporator, a condenser for liquefying the withdrawn refrigerant, means for translating air exterior of said zone in heat transfer relation with the condenser for abstracting heat from the same, whereby the temperature of the condensed refrigerant varies with variations in the temperature of said air, a capillary tube for conducting condensed refrigerant from the condenser to the evaporator, a heat conducting member disposed in heat transfer relation with a portion of the capillary tube whereby heat is imparted to the member at rates vary ing with the temperature of said exterior air,v

said member being disposed in heat transfer relation with the refrigerant in the evaporator whereby heat is abstracted from the member at rates varying with the temperature of the evaporator, and means responsive to the temperature of a portion of the heat conducting member for controlling the operation of the refrigerant withdrawing means.

7. In refrigerating apparatus, the combination of means defining a zone to be cooled, a refrigerant evaporator for abstracting heat from said zone, means for withdrawing vaporous refriger- =ant from the evaporator, a condenser for lique- 'fying the withdrawn refrigerant, means for translating air exterior of said zone in heat transfer relation with the condenser for abstracting heat from the same, whereby the temperature of the condensed refrigerant varies with variations in the temperature'of said air, an expansion device having an elongated passage of fixed fiow area for conveying condensed refrigerant from the condenser to the evaporator, a heat conducting member disposed within said zone and in heat transfer relation with a portion of the expansion device adjacent the inlet end thereof whereby heat is imparted to said member at rates varying with the temperature of said exterior air, said member being disposed in heat transfer relation with the refrigerant in the evaporator whereby heat is withdrawn from the member at rates varying with the temperature of the evaporator, and means responsive to the temperature of the heat conducting member for controlling the operation of the refrigerant with` drawing means.

8. In refrigerating apparatus, the combination of means defining a zone to be cooled, a refrigerant evaporator for abstracting heat from said zone, means for withdrawing vaporous refrigerant from the evaporator, a condenser for liquefying the withdrawn refrigerant, means for translating air exteriorly of said zone in heat transfer relation with the condenser for abstracting heat from' the same, whereby the temperature of the condensed refrigerant varies with variations in the temperature of said air, an expansion device having an elongated passage of fixed flow area for conveying condensed refrigerant from the condenser to the evaporator, a heat conducting member disposed in heat transfer relation with a portion of the expansion device adjacent the inlet end thereof whereby heat is imparted to said member at rates Varying with the temperature of said exterior air, said member being disposed in heat transfer relation with a portion of the evaporator, whereby heat is withdrawn from the member at rates varying with the temperature of the evaporator, means for adjusting the expansion device relative to the member, and means responsive to the temperature of the member for controlling the operation of the refrigerant withdrawing means.

9. In refrigerating apparatus, the combination of vmeans defining a zone to be cooled, a refrigerant` evaporator for abstracting heat from said zone, means for withdrawing vaporous refrigerant from the evaporator, a condenser for liquefying the withdrawn refrigerant, means for translating air exterior of said zone in heat transfer relation with the condenser for abstracting heat from the same, whereby the temperature of the condensed refrigerant Varies with variations in the temperature of said air, an expansion device having an elongated passage of fixed ow area for conveying condensed refrigerant from the condenser to the evaporator, a heat conducting member disposed within said zone and in heat transfer relation with a portion of the expansion device adjacent the inlet end thereof, said member being disposed in heat transfer relation with the evaporator, means for adjusting the member relative to the evaporator whereby the rate of heat transfer therebetween is varied, and means responsive to the temperature of the heat conducting member for controlling the operation of the refrigerant withdrawing means.

10. In refrigerating apparatus, the combination of means defining a zone to be cooled, a reperature of the condensed refrigerant varies with variations in the temperature of said air, a capillary tube for conveying condensed refrigerant from the condenser to the evaporator, a heat conducting member disposed within said zone and in heat transfer relation with a portion of the capillary tube adjacent its inlet end, whereby heat is imparted to said member at rates varying with the temperature of said exterior air, said member being disposed in heat `transfer relation with a portion of the evaporator, whereby heat is withdrawn from the member at rates varying with the temperature of the evaporator, thermostatic means for controlling the operation of the refrigerant withdrawing means and including a thermal responsive element disposed in heat transfer relation with the heat conducting member, and means for adjusting the thermoresponsive element relative to the heat conducting member.

11. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstracting heat from said zone. and including an inlet conduit for liquid refrigerant, a condenser, means for passing air exteriorly of said zone in heat transfer relation with the condenser for cooling the same whereby the temperature of 'the condensed refrigerant varies with variations in temperature of the air, means for translating vaporous refrigerant from the evaporator to the condenser for liquefaction therein, a capillary tube for conveying the condensed refrigerant from the condenser to said evaporator inlet conduit, a member disposed in heat transfer relation with the evaporator inlet conduit and the inlet end of said capillary tube whereby heat is abstracted from the member at rates varying with the temperature of the refrigerant in the evaporator and heat is imparted to the member at rates' varying with the temperature of the liquid refrigerant in the condenser, and means for controlling the operation of the refrigerant translating means in response to the temperature of said member.

l2. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstracting heat from said zone and including a portion of relatively small heat storage capacity spaced therefrom, means' for condensing refrigerant vaporized in the evaporator, a heat conducting member in heat transfer relation with said evaporator portion and a thermostat for controlling the operation of the refrigerant condensing means and including a thermal responsive element disposed in heat transfer relation with said heat conducting member, and means for imparting heat to said thermal responsive element in amounts varying with the temperature of the atmosphere exteriorly of said compartment.

13. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstracting heat from said zone, means for condensing at relatively high pressure refrigerant vaporized in the evaporator at relatively low pressure, a thermostat for controlling the operation of the refrigerant condensing means and including a. thermal responsive element spaced from the evaporator and responsive to the temperature thereof, and means for imparting heat to said thermal responsive element other than through the medium in the zone to be cooled and in amounts varying with the temperature of the atmosphere exteriorly lof the refrigerated zone.

14. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstracting heat from said zone, means for condensing at relatively high pressure refrigerant vaporized in the evaporator at relatively low pressure and a thermostat for controlling the operation of the refrigerant condensing means and including a thermal responsive element, said thermal responsive element being disposed in heat transfer relation with the high pressure and low pressure condensed refrigerant prior to its admission to the evaporator.

15. In refrigerating apparatus, the combination of means defining a zone to be cooled, an evaporator for abstrating heat from said zone, means for condensing at relatively high pressure refrigerant vaporized in the evaporator at relatively low pressure, means for conveying the condensed refrigerant from the condenser to the evaporator and including means for reducing the pressure of the refrigerant from its condensing pressure to its pressure of vaporization and a thermostat for controlling the operation of the condensing means and including a thermal responsive element, said refrigerant conveying means being disposed in heat transfer relation with the thermal responsive element so that heat is transferred between the thermal responsive element and the high and low pressure condensed refrigerant prior to the admission of the condensed refrigerant to the evaporator.

16. In refrlgerating apparatus, the combination of means for defining a zone to be refrigerated, an evaporator for abstracting heat from the media in said zone and including a portion of relatively small mass, means for circulating .refrigerant through the evaporator, a thermostatic device for controlling the operation of the `circulating means and including a heat-respontion of means for defining a zone to be refrigerated, cooling means for abstracting heat from the media in said zone and having associated therewith a portion of relatively small mass. means' for circulating refrigerant through the cooling means, a thermostatic device for controlling the operation of the circulating means and including a heat responsive element disposed in heat transfer relation `with the medium in said zone and a heat conducting member connecting said device and the portion of the cooling means of relatively small mass for conducting heat therebetween.

RAYMOND E. TOBEY. 

